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Biomedical subjects

J Iwata

Publications and source records attributed to J Iwata.

At least 109 records · Page 6Linked to original sources
PubMed1988

Different projections of the central amygdaloid nucleus mediate autonomic and behavioral correlates of conditioned fear.

The purpose of the present study was to determine whether lesions of areas projected to by the central amygdaloid nucleus (ACE) would disrupt the classical conditioning of autonomic and/or behavioral emotional responses. The areas studied included 3 projection targets of the ACE: the lateral hypothalamic area (LH), midbrain central gray (CG) region, and bed nucleus of the stria terminalis (BNST). Lesions were made either electrolytically or by microinjection of ibotenic acid, which destroys local neurons without interrupting fibers of passage. Two weeks later, the animals were classically conditioned by pairing an acoustic stimulus with footshock. The next day, conditioned changes in autonomic activity (increases in arterial pressure) and emotional behavior ("freezing," or the arrest of somatomotor activity) evoked by the acoustic conditioned stimulus (CS) were measured during extinction trials. Electrolytic and ibotenic acid lesions of the LH interfered with the conditioned arterial pressure response, but did not affect conditioned freezing. Electrolytic lesions of the rostral CG disrupted conditioned freezing but not conditioned changes in arterial pressure. Ibotenic acid injected into the rostral CG reduced neither the arterial pressure nor the freezing response. Injection of ibotenic acid in the caudal CG, like electrolytic lesions of the rostral CG, disrupted the freezing, but not the arterial pressure response. Injection of ibotenic acid into the BNST had no effect on either response. These data demonstrate that neurons in the LH are involved in the autonomic, but not the behavioral, conditioned response pathway, whereas neurons in the caudal CG are involved in the behavioral, but not the autonomic, pathway. Different efferent projections of the central amygdala thus appear to mediate the behavioral and autonomic concomitants of conditioned fear.

Amygdala↗
PubMed1988

[Graft patency and myocardial viability after aorto-coronary bypass surgery evaluated by exercise 201T1 myocardial SPECT].

To evaluate graft patency and myocardial viability after aorto-coronary (AC) bypass surgery, 58 patients (29 with old myocardial infarction and 29 with effort angina) underwent symptom-limited exercise 201T1 myocardial SPECT using a bicycle ergometer before and after surgery. The results were as follows: 1. The overall angiographic graft patency was 87% (97 of 112 grafts). 2. According to the stress SPECT images, graft patencies were 98% for areas with postoperative improvement by 201T1 uptakes, 79% for areas with unchanged patterns, and 53% for areas with worsened patterns. In spite of patent grafts, among cases with worsened 201T1 uptakes the etiologies included perioperative infarction, anastomotic strictures, and poor run-off distal to the anastomoses. 3. Following patency of grafts, postoperative normalized perfusion patterns were observed in 69% (27 of 39 segments) of segments with persistent preoperative low uptakes and 25% (4 of 16 segments) of segments with persistent preoperative defects. Thus, exercise 201T1 myocardial SPECT proved a useful diagnostic means of assessing graft patency and effectiveness. However, after AC bypass surgery, 25% of the regions which had persistent defects before surgery exhibited normal perfusion patterns. These findings suggest that persistent defects may represent hypoperfusion of viable myocardium, and that we should carefully diagnose myocardial scars.

Adult↗
PubMed1987

Cardiovascular responses elicited by stimulation of neurons in the central amygdaloid nucleus in awake but not anesthetized rats resemble conditioned emotional responses.

Cardiovascular responses elicited by electrical stimulation of the central amygdaloid nucleus were examined in awake and anesthetized rats. Stimulation through chronically implanted electrodes evoked increases in arterial pressure and heart rate in awake, freely behaving rats. The responses, which were dependent upon the frequency and the intensity of the stimulus, were not consistently related to the presence of evoked amygdaloid afterdischarges or to evoked behavioral reactions. Following induction of anesthesia, stimuli delivered to the same rats through the same fixed electrodes produced decreases in blood pressure and heart rate. Microinjection of L-glutamate into the amygdala of freely behaving rats also elicited increases in arterial pressure and heart rate, indicating that the cardiovascular changes evoked by electrical stimuli are due to excitation of local neurons rather than fibers of passage. The timing and pattern of the response elicited by electrical stimulation of the amygdala in the awake but not the anesthetized rat closely corresponds with that evoked by an acoustic conditioned emotional stimulus.

Action Potentials↗
PubMed1987

[Chondromyxoid fibroma of the skull base extending from the middle fossa to the posterior fossa--case report].

An extremely rare case of chondromyxoid fibroma of the skull base extending from middle fossa to posterior fossa is reported. The patient is a forty-seven year old woman who became paranoiac four months before admission and her gait was unsteady for one month. On April 27th, 1985, she fainted and was admitted to Kanto Rosai Hospital on April 30th. She was drowsy and disoriented. Neurologic examination revealed left pyramidal tract signs and impaired functions of right Vth (first and second branches), VIth and VIIIth cranial nerves. She was anemic and bleeding tendency due to thrombocytopenia was also recognized. Hematologist's diagnoses were myelodysplastic syndrome plus iron deficiency anemia. Neuroradiologic studies including CT scan, cerebral angiographies and MRI revealed a huge extra-axial skull base tumor extending from middle fossa to posterior fossa completely destroying the skull base. Stenosis of cavernous portion of internal carotid artery due to tumoral involvement was also noted. Surgical excision of the tumor was performed three weeks after the admission with the use of platelet transfusion. Transpetrosal transtentorial approach was performed removing the intracranial part of the tumor which was a semi-translucent jelly-like soft mass. The patient had a good post-operative course and improvement in the neurologic condition was recognized. Microscopically, the tumor showed marked lobular formation with small vessels and fibroblasts in the periphery of the lobule. The fibroblasts took stellate figures in the myxoid matrix at the center of the lobule. Chondroid pattern was also observed. Mitosis and nuclear atypism were not observed. Histological diagnosis was chondromyxoid fibroma.(ABSTRACT TRUNCATED AT 250 WORDS)

Cerebral Angiography↗
PubMed1986

Intrinsic neurons in the amygdaloid field projected to by the medial geniculate body mediate emotional responses conditioned to acoustic stimuli.

In previous experiments we implicated projections from the medial geniculate body (MG) to a subcortical field, involving portions of the posterior caudate-putamen and amygdala, in the classical conditioning of emotional responses to acoustic stimuli in the rat. In the present series of experiments we examined whether intrinsic neurons in the subcortical field mediate emotional conditioning and, if so, whether the critical neurons are contained within the amygdala or the caudate-putamen. Rats were prepared with a unilateral electrolytic lesion of the MG. Contralaterally, intrinsic neurons were destroyed in the subcortical field by microinjection of ibotenic acid. This lesion combination leaves one MG and one subcortical field intact but disconnected. Controls received unilateral injection of phosphate buffer vehicle into the subcortical field contralateral to the MG lesion or were unoperated. After two weeks the animals were instrumented for continuous, computer-assisted recording of arterial pressure and heart rate and subjected to classical conditioning trials involving the presentation of a pure tone in association with foot-shock. The occurrence of the shock with respect to the tone was random for a pseudoconditioned control group. Conditioned changes in mean arterial pressure, heart rate and emotional behavior ('freezing') elicited by the tone were assessed during extinction trials. Following completion of the experiments, the rats were sacrificed and their brains were removed and sectioned using standard procedures. Lesion location and size was evaluated with the assistance of a computer-based image processing system. In unoperated conditioned rats the acoustic stimulus elicited increases in arterial pressure and heart rate, and induced freezing. The arterial pressure and freezing responses differed in conditioned and pseudoconditioned rats, but the heart rate response did not. Therefore, only the arterial pressure and freezing responses reflect the formation of an association between the tone and shock. Destruction of intrinsic neurons in the subcortical field contralateral to a unilateral MG lesion disrupted the associative conditioning of the arterial pressure and freezing responses. These were reduced in magnitude to the level observed in pseudoconditioned rats. The non-associative heart rate change was not affected by the lesions. That ibotenic acid destroyed intrinsic neurons and spared fibers in the subcortical field was demonstrated anatomically and biochemically.(ABSTRACT TRUNCATED AT 400 WORDS)

Amygdala↗
PubMed1986

Disruption of auditory but not visual learning by destruction of intrinsic neurons in the rat medial geniculate body.

The contribution of intrinsic neurons in the medial geniculate body (MG) of the rat to the classical conditioning of emotional responses to acoustic stimuli was examined. Injection of ibotenic acid, which destroys cell bodies but not axons of passage, into the MG disrupted the conditioned changes in mean arterial pressure and emotional behavior elicited by a tone previously associated with footshock. Unconditioned responses elicited by the tone and by the footshock were unaffected. Moreover, the same animals readily learned to associate a visual stimulus with footshock. Thus, destruction of intrinsic neurons in the MG selectively disrupts the conditioning of emotional responses to acoustic stimuli. The MG appears to be the afferent link in a modality specific emotional learning pathway.

Acoustic Stimulation↗
PubMed1986

Destruction of intrinsic neurons in the lateral hypothalamus disrupts the classical conditioning of autonomic but not behavioral emotional responses in the rat.

The present study examined whether destruction of intrinsic neurons in the lateral hypothalamus of the rat would disrupt the acquisition of classically conditioned changes in arterial pressure. Ibotenic acid, a cellular toxin which spares axons of passage, was injected bilaterally in the hypothalamus either medial or lateral to the fornix. After 2 weeks the animals were subjected to classical fear conditioning trials involving the presentation of a tone in association with footshock. The next day changes in arterial pressure and emotional behavior elicited by the tone alone were measured. Destruction of intrinsic neurons in the lateral hypothalamus prevented the normal establishment of the arterial pressure conditioned response but did not affect the behavioral response. Unconditioned arterial pressure responses elicited by the tone and shock were not affected. Medial hypothalamic injections had no effect on any of the responses. The location of the lateral hypothalamic cell loss overlapped with the neurons projecting to the autonomic region of the spinal cord. Intrinsic neurons in the lateral hypothalamus therefore appear to be specifically involved in mediating learned cardiovascular adjustments.

Animals↗
PubMed1986

Interruption of projections from the medial geniculate body to an archi-neostriatal field disrupts the classical conditioning of emotional responses to acoustic stimuli.

We have previously found that the coupling of changes in autonomic activity and emotional behavior to acoustic stimuli through classical fear conditioning survives bilateral ablation of auditory cortex but is disrupted by bilateral lesions of the medial geniculate nucleus or inferior colliculus in rats. Auditory fear conditioning thus appears to be mediated by the relay of acoustic input from the medial geniculate nucleus to subcortical rather than cortical targets. Since the medial geniculate nucleus projects, in addition to auditory cortex, to a striatal field, involving portions of the posterior neostriatum and underlying archistriatum (amygdala), we have sought to determine whether interruption of connections linking the medial geniculate nucleus to this subcortical field also disrupts conditioning. The conditioned emotional response model studied included the measurement of increases in mean arterial pressure and heart rate and the suppression of exploratory activity and drinking by the acoustic conditioned stimulus following delayed classical conditioning, where the footshock unconditioned stimulus appeared at the end of the conditioned stimulus. The peak increase in arterial pressure and the duration of activity and drinking suppression were greater in unoperated animals subjected to delayed conditioning than in pseudoconditioned controls, where the footshock was randomly rather than systematically related to the acoustic stimulus. Increases in heart rate, however, did not differ in conditioned and pseudoconditioned groups. While the arterial pressure and behavioral responses therefore reflect associative conditioning, the heart rate response does not. Rats were prepared with bilateral lesions of the medial geniculate nucleus, bilateral lesions of the striatal field or asymmetrical unilateral lesions destroying the medial geniculate nucleus on one side and the striatal field on the contralateral side. The latter preparation leaves one medial geniculate nucleus and one striatal field intact but disconnected and thus produces a selective auditory deafferentation of the intact striatal field. Control groups included animals with unilateral lesion of the medial geniculate nucleus, with unilateral lesion of the medial geniculate nucleus combined with lesion of the ipsilateral striatal field, unilateral lesion of the medial geniculate combined with lesion of the contralateral anterior neostriatum (a striatal area outside of the medial geniculate nucleus projection field).(ABSTRACT TRUNCATED AT 400 WORDS)

Acoustic Stimulation↗
PubMed1986

Direct determination of sulfate conjugates of 17-oxosteroids in urine by liquid chromatography.

We describe a new liquid-chromatographic method with fluorescence detection for direct simultaneous determination of four urinary sulfate conjugates of 17-oxosteroids (17OS), without use of solvolysis or enzymatic hydrolysis. The 17OS sulfates in urine samples are extracted with benzene as ion pairs in the presence of benzyltributylammonium chloride. These ion pairs are converted to hydrazones by use of dansyl hydrazine in trichloroacetic acid solution and then are separated by liquid chromatography. The proposed method, being simple and rapid, shows a good separation of 17OS sulfates and superior sensitivity, sufficient recovery, and good reproducibility.

Androsterone↗
PubMed1984

Mechanism of neutrophil chemiluminescence induced by wheat germ agglutinin: partial characterization of the antigens recognized by wheat germ agglutinin.

Wheat germ agglutinin (WGA) stimulated neutrophils to produce significant levels of luminol-dependent chemiluminescence (CL). Since WGA is known to bind N-acetylglucosamine (GlcNAc) oligomers and N-acetylneuraminic acid (NANA), we attempted to determine which binding property of WGA is essential for induction of CL. The succinylated form of WGA (SuWGA), which is no longer able to bind NANA, was still able to induce CL. N-Acetylglucosamine at a concentration of 20 mmol/L almost completely inhibited WGA-induced CL production by neutrophils, whereas bovine submaxillary gland mucin, a potent blocker of NANA binding of WGA, failed to inhibit CL production. Lectins with the GlcNAc-binding property were examined for their ability to induce CL. Those that have higher valences and have a tendency to bind GlcNAc oligomers in the internal portion of glycoconjugates were able to induce CL, whereas those that have low valences and bind terminal GlcNAc of glycoconjugates failed to induce CL even at high concentrations. Attempts were made to characterize the neutrophil membrane proteins recognized by WGA. Glycoproteins with a molecular weight of 25,000 daltons were identified by a 50 mmol/L GlcNAc elution of WGA gels loaded with 125I-labeled neutrophil membrane proteins. Elution with 500 mumol/L GlcNAc trimer produced several glycoproteins of different molecular weights in addition to the glycoproteins of 25,000 daltons. 125I-labeled WGA and SuWGA were used for autoradiographic analysis of cell extracts of the neutrophils separated on sodium dodecyl sulfate polyacrylamide gels. WGA recognized multiple glycoproteins of different molecular weights, whereas SuWGA bound only a few of them. Glycoproteins of 25,000 daltons, probably corresponding to those identified by 50 mmol/L GlcNAc elution, were also recognized.

Antigens↗